Amplifying apparatus



1,636,699 juiy 26, 1927. L" V LEwls AMPLIFYING APPARATUS Filed July 1,1924 INVENTOR: I -g WWW, a; x W

M ATTORNEY Patented July 26, 1927.

i.,lS36,699

UNETED STATES PATENT OFFIE.

LLOYD "V. LEWIS, OF EDGEWO OD BOROUGH, PENNSYLVANIA, ASSIGNOR TO THEUNION I SWYTCH & SIGNAL COMPANY. 01? SWISSVHLE, PENNSYLVANIA, ACORPRATION or rnnnsvnvsnm.

A MPLIFYING API'AB-ATUS. 1

Application filed July 1,

My invention relates to amplifying apparatus, and particularly toamplifying apparatus including a three element electron tube.

One purpose of my invention is to provide an arrangementof apparatuswhich will automatically compensate for variations in the voltage of theuni-directional current supply of a three element electron tubeamplifier so that its alternating current output will not be affected bysuch variation.

T will describe one form and arrangement of apparatus emhoclving myinvention. and

will then point out the novel features thereof in claims. v

The accompanying drawing is a diagram matic view showingone form ofamplifying apparatus embodvingz my invention.

Referring to this drawing. the apparatus comprises an electron tuhe Ahaving a tilament 1, a grid 2. and a plate 3. The source of the energyto be amplified is here shown as a winding 4 tuned by a condenser 14 andin inductive relation with a railway track rail 5 in which alternatingcurrent is assumed. to he flowing.

Filament l is supplied with current "from a suitable source oi directcurrent. such as a generator G. and a regulating resistance 7 isinterposed hetween the negative terminal of generator G and the filamentl. The grid 2, is connected. through winding 4 with resistance 7. thisresistance serving to regulate the amount of negative grid bias of thetube A, which negative bias is prcterahly made greater than the peakvalue of the alternating current voltage normally supplied by coil 4.Voltage is applied to the plate circuit by a dynamotor D that is, arotat ing machine having a low voltage winding: 9 and a high voltageWinding 8 on the same armature and a field winding 13 for supplyingmagnetic flux to both windings. The low voltage winding 9 and the fieldwinding 13 are connected in parallel with generator G. One terminal ofwinding 9 is connected directly with filament l and the other terminalor this winding is connected. through primary 10 of a transformer '11with plate 3 of tube A. Secondary 11 of transformer T is connected withthe device 12 to which it is desired to supply the amplified energy. Thedevice 12 may he a relay, as here shown 1924. Serial No. 723,602.

or'mav be any other suitable form electrical apparatus.

The operation of an electron tube amplifier is well understood by thoseskilled" in the art, and for present purposes it is only necessary tostate that the alternating voltage induced in winding 4 is applied tothe grid of tube A, is amplified, and causes a current of similarcharacteristic but increased amplitude to be superposed upon the directcurrent supplied to the plate circuit by winding 8 of dynamotor D. Thea1- ternatmgr component of the current flowing In the plate circuit istransferred to device 12 by transformer T.

Under some conditions of operation considerahle fluctuation may occur inthe voltage of generator G. With only the apparatus thus far described,this fluctuation would have three results. First, it would vary thetemperature of filament 1; second, it would vary the negative bias ofgrid 2; and third, it would vary the speed of dynamotor D and hence theoutput voltage of winding 8. All three of these things would vary theamount of alternating current supplied to device 12.

This is undesirable, and to prevent its 00- currence I interpose aballast lamp 6 between resistance 7 and filament 1. This lamp maycomprise an iron wire filament in a low res sure hydrogen atmosphere, ormay be 0 any suitable type having the characteristic of increasing itselectrical resistance with increase of voltage applied thereto; so thatit tends to maintain the current through filament 1 and resistance 7constant over a considerable range of applied voltage On account 01 thischaracteristic, therefore, a given increase in the voltage of generatorG will cause a substantially equal increase in the voltage drop acrosshallast lamp 6, and in the negative bias of grid 2 with respect tofilament 1, because the ballast lamp is in the circuit hctween grid 2and filament 1.

Dynamotor D is preferably so wound that its turn ratio, that is. theratio of the. turns in windings 9 and 8, is substantially equal to theamplification constant-of tube A.

I will assume that the apparatus is so proportioned and adjusted as togive proper o oration at normal voltage of generator and that the tube Ahas an amplification constant of 8. It now the voltage of generator Gvaries, as by an increase oi? one volt, the ballast iamp 6 willmaintain. a constant current through the iiiement 1 and the mega tivebias of gridQ will be increased by one volt. This Wili manifestly tendto tlecreose the plate potential by on amount co l-iii to the change ingrid hies muitipiieci by the am lificotion constant of the tube, thatis, eig, t volts. But the increase oi one volt in the electromotiveforce of generator *3 also tends to increase the .voitege of: winding 8of dynamotor D by eight volts and hence the decrease causevi by theii'icreaseti liege. tive grid bias compensates for the increased voltagedelivered by the dynemotor and the just the converse of that descrihetiehov and will be understood. without forthei" planetion.

It is evident that it is not esscotiel that the dynamoto'r chromatic heexactly the some as the amplification coiustoot oi the tube but that anetlventegeous cooig iehsetion will be provided by this arrangement ofepporz tus in greater'or less degree whatever the re lation betweenthese two factors may he Amplifying epperetus emhociyihg toy in ventionis particularly adapted for, though i'o o way limited to, application tomiiwey tiefiic controlling apparatus in which train carcied governingmechanism is controlled by energy received from. the tmchvvey.

Although I have heroic shown and de scribed only one form of amplifyingapple teoeeoo rotusemhodying my invention, it is linden stood thatvarious changes and modifications may he made therein within the scopeof the appended claims without departing from the spirit and scope of myinvention.

Having thus described my invention, what I claim is:

l. in combination, an "electron. illliQ, at source of direct currentvoltage connected with. the filament of schituhc, o ballast lampinterposed between said moment and the negative terminal of said source,a grid cirsuit.- for the tube including said holiest lamp, and adynamotor energized from. source M16; having it turn ratio equal to theampliticeticn constant'oi said tube-tor spipplying voltage to the pietecircuit of said. tube 2.. In combination, an electron. tube, o source ofunidirectional filament current; o. holiest lamp interposed hot-Ween thenegative terminal of said source and the iiimnoot of sold tube, s grid.circuit for said tube in cluding seitl holiest lamp, anti :1 (lynamotorhaving one 'ivimiing connected; with we source and a second Windingihcludeci in the plate circuit of said tube, the dyhemotor being soconstructed that increase of one unit in the voltage of soloSOHECBGHHSQS the voltage in the plate circuit to increase by at numberof units equal 'to the amplification constant of said tube.

ii. in combinotice an electron tube, a, som'ce of direct currentvoitcge' connected with the filament of said tube 9, lmiiest lsi'opinterposed hetweci'i said. filament and the negative terminal of saidsource, a grid cir-- cuit for the tube including ssicl holiest lamp, andmeans for supplying" the plate circuit of said tube with voltage derivedfrom am proportional to said direct current'voitege.

in testimony whereof I afiix my signs, tore.

LLQYD V. LE'WKS.

